To elaborate just a bit on Phil's correct answer:
Hot to hot = doubled voltage.
Hot-to-ground = half-voltage.
https://img.bhs4.com/e7/1/e71df333b1...e9a5_large.jpg
One side will be - to ground +.
One side will be + to ground -.
To see this in action - exactly this - look at the filament voltage schematic for a Dynaco PAS. As these are all dumb components, loading does not change anything - to the capacity of the source in any case.
Peter Wieck
Melrose Park, PA